green_mask
green_div = 256 / (cm.green_mask + 1);
green_mul = 256 / (cm.green_mask + 1);
cm->green_mask = 0x0F;
cm->green_mask = 0x0FF;
cm->green_mask != vcm->green_mask ||
cm->green_mask = vcm->green_mask;
cm->red_mask = cm->green_mask = cm->blue_mask = 0x3f;
cm->red_mask = cm->green_mask = cm->blue_mask = 0xf;
cm->red_mask + 1, cm->green_mask + 1, cm->blue_mask + 1);